This invention relates to an integrated injection logic semiconductor device having a lateral transistor and a vertical transistor.
Recently, much attention is paid to an Integrated Injection Logic (I.sup.2 L) semiconductor device simpler in structure and higher in manufacturing yield and higher in integrated degree than a Transistor Transistor Logic, TTL. This I.sup.2 L is called also "MTL". The I.sup.2 L semiconductor device is constructed such that its semiconductor substrate is provided with a switching transistor and an injector for injecting minority carriers into the base region of the switching transistor; and while the minority carriers are being injected into the base region of the switching transistor, the input of the I.sup.2 L device is so controlled as to effectively control the output of the I.sup.2 L device, i.e., the collector of a vertical transistor of the I.sup.2 L device.
In a conventional I.sup.2 L semiconductor device, an N type semiconductor layer is formed in the semiconductor substrate by vapor epitaxial growth method and first and second P type regions formed by selectively diffusing boron into the N type semiconductor layer at a rate of about 10.sup.17 to 10.sup.19 atoms/cm.sup.3 are provided in the N type semiconductor layer. Phosphorus is diffused into the first P type region at a rate of about 10.sup.19 to 10.sup.21 atoms/cm.sup.3 to form an N type region in this first region.
In the I.sup.2 L semiconductor device having the foregoing structure, a lateral PNP transistor is composed of the second P type region (emitter), N type semiconductor layer (base) and first P type region (collector), and a vertical NPN transistor is composed of the N type semiconductor layer (emitter), first P type region (base) and N type region (collector). In the I.sup.2 L semiconductor device, since, as above described, an N type semiconductor layer region widened downwardly fanwise between the first and second P type regions is used as the base of the lateral transistor, the transport efficiency of carriers supplied from the injector is not sufficient. Further, the base layer of the lateral PNP transistor is commonly used also as the emitter layer of the vertical NPN transistor, and if therefore, the injection and transport efficiencies of one transistor are improved, those of the other transistor will be deteriorated with the result that the synthetic efficiency of the semiconductor device is not improved to a greater extent than specified. Further, since the emitter of the vertical transistor is formed of an N type semiconductor layer, the impurity concentration of the vertical transistor can not but be made lower than that of the base region of the vertical transistor. This is also one of causes of deteriorating the injection and transport efficiencies of the transistor.